docs: def create_cached_data_dir():
      '''
      Returns the path to the data directory to download CF standard names.
      Use $XDG_DATA_HOME.
      '''
      writable_directory = os.path.join(os.path.expanduser('~'), '.local', 'share')
      data_directory = os.path.join(os.environ.get("XDG_DATA_HOME", writable_directory),
                                    'compliance-checker')
      if not os.path.isdir(data_directory):
          os.makedirs(data_directory)
  
      return data_directory